Some of mine would be:
BG 1:
"I will be the last! And you will go first *maniac laughter*"
Sarevok, BG 1 intro
"I be Thalantyr, mighty mage of Beregost!"
Thalantyr, greeting
"Heya, it's me, Imoen"
Imoen, first meeting.
"We are all doomed!"
Xan, generic depressed comment
"WHA... *cough* Yes?"
Khalid, generic comment
"Nature's servant awaits"
Jaheira, generic comment
"Go for the eyes Boo, go for the EYES ARGH!"
Minsc, battle cry
"No, we're not mercenaries. We just carry weapons and kill things for the joy of the experience."
Protagonist
BG 2:
"I cannot be caged!
I cannot be controlled!
Realize this as you die ever pathetic, ever fools."
Irenicus, breaking free in Spellhold.
"Here mousey mousey!"
Bhodi, hunting you in Spellhold
There are dozens more tough.
I absolutely adore Jan's stories but they are too voluminous to count as "quotes".